The present invention relates to an apparatus for automatically initiating the drop of a neutron absorbing member into the core of a nuclear reactor.
More specifically, the apparatus according to the invention makes it possible to automatically free from its control mechanism an absorbing member, when the level of the cooling liquid circulating in the vessel containing the reactor core drops below a minimum level.
In nuclear reactors, scram of the fission reaction in the reactor core is obtained by dropping neutron absorbing members into the latter.
In pressurized water nuclear reactors, these absorbing members are generally in the form of a cluster or a control rod. They are suspended on a control bar, which is itself connected to a manipulating member by an electromagnetic link. By controlling the fracture of this link, the absorbing members automatically drop into the reactor core and consequently bring about the scram of the fission reaction. Experience has shown that these scramming systems have a very high reliability level.
However, the information controlling scram passes through a complex electronic and mechanical apparatus chain and consequently it is not impossible for none of the absorbing members to drop into the reactor core.
Despite the highly improbable character of this hypothesis, it still leads to considering the existence of a scram system making it possible, by a direct mechanical action to automatically separate the absorbing member from its control bar when the cooling conditions impose reactor scram.